ENCODE-FM©

Electronic Nomenclature and Classification Of Disorders and Encounters for Family Medicine

ENCODE-FM is a systematic and hierarchical controlled clinical terminology for family medicine, intended for use in electronic medical records. ENCODE-FM was derived from our knowledge of ICPC, ICD-10, the ICPC alphabetical index and our 15 year experience with clinical family medicine and a computerized vocabulary based on ICHPPC-2.

ENCODE-FM has been designed expressly for use at point of service in primary care. We have addressed the issues of ease of data entry and accuracy of aggregate data retrieval in its design, the mapping to other classifications, and choice of words and terms.

Published research (J. Amer. Medical Informatics Assoc. 3(3): 224-233, 1996) has shown that none of the large nomenclatures intended to cover the whole health care system, each of over 100,000 terms, covers all clinical content or even all diseases. On the other hand ENCODE-FM makes no claim to be an overarching nomenclature of medicine. It was designed to do one part of that task well - namely to be a CLINICAL terminology of ONLY symptoms, complaints, diagnoses, disorders and reasons for encounter for use in primary care electronic records.

Since it is obvious that all possible terms cannot be included in ENCODE-FM, the question arises of how to deal with rare diagnoses and terms which a clinical practitioner cannot find. We propose the following mechanism:

1. Vendors of electronic records must maintain a "failed lookup" table in which any term not found is recorded and fed back to the authors of ENCODE-FM;

2. The authors will take all failed lookups, add terms as clinically relevant to ENCODE-FM, and map ALL terms to ICPC and ICD-10;

3.Those terms added to ENCODE-FM will become part of its next revision;

4. All terms which are considered rare enough will not be included in future revisions BUT the onus is on the vendor using ENCODE-FM, by appropriate programming, to continue to allow their use locally by the individual physicians who need them;

5. All such terms maintained locally MUST be exportable with the relevant patient records, and searchable by using the ICPC and ICD-10 maps;

6. Vendors who use ENCODE-FM will agree in their liscencing agreement to the above regulations.

ENCODE-FM contains 9274 terms. Of these, 60% cannot be uniquely identified by their ICPC/ICD-10 number combination, i.e. are totally unique to ENCODE-FM.

It includes the myriad of terms for reasons for encounter. These terms are not part of the ICD-10 scheme and their exclusion makes ICD a poor vocabulary for primary care. Since in primary care the reason for encounter determines much of the downstream cost of care, having the ability to record it allows more meaningful analysis of patterns of health care.

It includes relevant terms in local use either as hierarchical categories or as synonyms. Terms have been written where necessary to reflect clinical linguistic usage.

All terms can be accessed by using ICPC however the classification terms in ENCODE-FM 2.0 are often modified from the ICPC terms. For instance "Sympt/complt mouth/tongue/lip (D20)" was split to become Symptom/Complaint of mouth; Symptom/Complaint of tongue; Symptom/Complaint of lips, each with a unique code number and each with more specific terms and synonyms underneath. All three headings AND their associated hierarchy of terms would by found by searching for the ICPC D20 code, yet they are split for purposes of having more specificity in the clinical record.

In addition to symptoms and complaints, diseases and disorders, ENCODE-FM has terms in appropriate chapters for the following:

• risk factors (e.g. risky sexual behaviour)
• family history of illness (e.g. family history of thalassemia)
• external causes of morbidity (e.g. abused child)
• reasons for encounter, other than symptoms and diseases (e.g. request for driver's form/examination)

In designing a terminology, decisions and compromises must be made to prevent the malignant spread of unnecessary terms, and to maintain a standard mode of expression. In most cases these compromises do not affect the users' ability to find and choose an appropriate term.

We expressly considered all terms in ICD-10 but not all ICD-10 terms have been mapped. Only those which are clinically relevant and which fit the criteria of being unambiguous, precise and exclusive, or which add useful variants to the synonym dictionary were included in the hierarchy of ENCODE-FM. Terms like "pneumonia in diseases classified elsewhere" were specifically excluded.

By convention, any term in ENCODE-FM that says "disorder of" does NOT include those disorders which are infectious, inflammatory, neoplastic, traumatic, or congenital. These are specified separately.

Correct international spellings are used for proper names and terms from other languages e.g. Folie à Deux. All other terms use American spellings, e.g. hematology not haemotology, esophagus not oesophagus, tumor not tumour.

Sometimes conflicts arose in the proper placement of a term. These conflicts tended to be between site and etiology - we chose to maintain the etiologic classification and intend to extend ENCODE-FM to classify by body site in the next revision.

Oftentimes the ICD-10 coding scheme requires double coding, especially in classifying infectious diseases, and the two codes are identified with a dagger or asterix in the ICD-10 book. Since we maintain a "one term-one map" policy, if one code provided greater specificity it was chosen as the best map to ICD-10. If neither code was specific, the one with the greatest clinical relevance was chosen. For example, gonococcal prostatitis has 2 possible ICD-10 codes - a54.2: "gonococcal pelviperitonitis and other gonococcal genitourinary infections" and n51.1: "disorders of prostate in diseases classified elsewhere". We chose to map it to a54.2 since clinically it was most relevant and specific. All of these potential double codings may be controversial and we welcome feedback from users. In either case, since the ENCODE-FM term is very specific (gonococcal prostatitis) BOTH of the ICD-10 maps can be derived from the ICD-10 publication by anyone interested in complete ICD coding.

The maps from ICPC to ICD-10 in ENCODE-FM usually but not always follow the published ICPC to ICD-10 conversion structure. (Lamberts H, Wood M, and Hofmans-Okkes I. eds. The International Classification of Primary Care in the European Community With a Multi-Language Layer. Oxford University Press, Oxford 1993.) In some cases the ENCODE-FM maps are more specific and we believe them to be a better fit. Issues of ICPC to ICD-10 mapping will ultimately be adjudicated at the WONCA Classification Committee and incorporated into future revisions of ENCODE-FM.

Terms are written in the singular, plurals are avoided unless clinically sensible (e.g. Intestinal Worms & Parasites).

We classified terms based on their customary clinical usage. This means for example that external and middle ear neoplasms are in the "Ear" chapter, but acoustic neuroma is in the neurological chapter.

STRUCTURE

The distributed file is in Microsoft Excel 5.0© format for IBM compatible computers. This file format may be converted by users to other formats as required.

There are 2 worksheets in the file: one which displays the hierarchy indented and the other in which all terms are in one column and the hierarchy can be inferred form the "level" identifier. The following table describes the different columns in the disk file - programmers may feel free to use any numbering scheme that best fits their application, however they are REQUIRED maintain the exact wording and the unique number since it will ALWAYS be assigned to that term.

The internal structure is organized first by body system as is ICPC. However we have added an 18th system chapter to address the specific issues of the perinatal and infancy period. Within each system chapter the terms are divided into categories of 1) symptoms and complaints, 2) general disorders, 3) infectious and inflammatory disorders, 4) benign and malignant neoplasms, 5) trauma and 6) congenital disorders. The separation of categories is maintained across all body system chapters and allows the user to find all e.g. infectious diseases of the neurological system simply and rapidly.

Terms are arranged in a hierarchy from general to specific within each etiologic category. There are up to 10 levels of hierarchy plus synonyms. This meant that the traditional structures of ICPC and ICD-10 - specific terms first, followed by "ragbags" (e.g. other diseases of the digestive system) - had to be inverted. Since no ragbag terms exist in ENCODE-FM the initial term in a hierarchical tree structure is the general term (e.g. general disorder of the respiratory system) under which are placed the specific terms in the hierarchy.

Each term in ENCODE-FM stands alone and can be used in an electronic record without reference to the rest of the terminology. There are no ragbags or terms with the modifiers "NOS", "NEC"; and only rarely "unspecified". There are no duplicate terms.

CONDITION:

• 1. Symptom/Complaint/Sign
• 2. General Disorder (not Infectious, Inflammatory, Neoplastic, Traumatic, Congenital)
• 3. Infection/Inflammation
• 4. Neoplasm Unspecified Benign or Malignant
• 5.Trauma
• 6.Congenital Anomaly/ Malformation

CONDITION

1

2

3

4

5

6

SYSTEM
A- General
B- Hematologic System
D- Digestive System
F- Eye and Adnexae
H- Ear
I - Perinatal or Infancy Period
K- Cardiovascular System
L- Musculoskeletal System
N- Neurological System
P- Psychology and Psychiatry
R- Respiratory System
S- Skin/Subcutaneous Tissue
T- Nutrition, Metabolism or the Endocrine System
U- Urinary System
W- Contraception or Obstetrics
X- Female Breast or Genital System
Y- Male Breast or Genital System
Z- Social

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FUNCTIONAL GUIDELINES

The following guidelines are suggested in recognition of the fact there are many possible user interfaces to a clinical terminology, and that the use of a terminology both clinically and for epidemiological recording requires that terms be chosen as much as possible without error.

1. The records system should ensure that the most appropriate term is displayed during a term search:

• by allowing the user to search for terms in the whole terminology; in each chapter; and by etiologic classification.
• by allowing natural language searching: the user types in a partial term and the system returns a list of terms with that text string, e.g. typing "catar" returns all types of cataracts and catarrh

2. The records system should allow the user to be "situated" in the terminology and ensure that a chosen term is the most appropriate: by allowing the user to walk through the hierarchical structure of terms:

• by allowing the user to walk through the hierarchical structure of terms.
• by displaying the location of the term in the hierarchy and at least one level above and below the term selected as well as synonyms of the primary term.
• by allowing the user to select any term from the displayed list.

3. The user of the record should be able to employ a term which s/he may not be able to find in the terminology. The computerized record should allow the user to add locally used terms and terms of increasing specificity at the time of data entry in such a way that:

• those terms are always retained in the record in a "failed look-up table".
• those terms can be mapped to ICPC and ICD-10 so that clinical classification can occur.
• the clinical terminology and classification tables are not contaminated by new terms which cannot be identified as such, and which have not been approved by the authors of the terminology.
• the new term can be used for alerts, prompts and reminders.

This will serve to allow individual idiosyncrasies and yet retain standardized information.

4. The records system should allow updating of the terminology without losing or changing previously recorded information.

The critical aspect is that the text rubric and unique number be retained exactly as it was recorded by the physician along with the ICPC and ICD-10 mapped codes.

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